My pump is directly off the battery (which is in passenger bin).

 

What lithium ion battery did you get? It needs to be correct for the application. They basically need to have on board charging management that can work with conventional alternators on old cars. A lithium ion battery does not charge the same way as a normal automotive lead acid battery.

 

I have:
https://shoraipower.com/lfx36l3-bs12--p130

"Shorai Batteries require a charging system output of 13.1 Volts or higher at idle, and must not exceed 15.2 volts at maximum output." I am thinking with a alternator in good working order, it should be in spec. Mine is going under and over that, which is why I am having it rebuilt. Assume it has a bad diode and or regulator.

and their proprietary charger:
https://shoraipower.com/sho-bms01-p134

 

Iceman did you add an additional diode? Or thats what your pumping out stock?
I added an adjustable diode. Diode was recommended by Xavier. I am hoping to add my other wire (battery to alternator) later today or at least by the end of this month.
I am excited to get this wrapped up as it is my final quirk of the car. The rest should all be play with an occasional new pretty piece here or there... I hope anyway!

 

That was on the stock alternator. Its currently @ IRP for their alternator upgrade. New diode and regulator.

 

Ok cool. We shall wait I guess....

 

I highly doubt this battery is going to work unless you literally don't try to charge it with an alternator and just drive the car for 30 minutes at a time, charging it with their proprietary charger (like a dedicated drag car). They have a proprietary charger for a reason. It's not meant for passenger vehicles with all those electrical loads and 100 amp alternators, it's meant as a starter battery for ATV's and stuff. There is nothing on that website that even hints that it is meant for a conventional passenger car.

It's even called a "Powersports battery" on their website. Yes I know that people around here use these tiny *** batteries (non LIthium) but as actual batteries, they all suck.

The only batteries that have ever worked on an Rx-7 like a normal car's normal electrical system are basically stock sized batteries in the stock location. I've had relocated dry cells, Miata batteries in the stock location (Miata batteries suck on actual Miatas), I've had friends with various motorcycle batteries etc. They all suck by the standards of "normal" cars that you can just start whenever, never have to put a tender on, and never have to worry about voltage. My stock '95 was like a Honda Accord of that era (in a good way). It just had a brand new mid priced 2 year warranty stock sized lead acid battery from Autozone. I never had any problems with it. I could leave the car for a month and start it when it was below freezing outside. It fired with no issues.

You guys are just asking too much of these tiny batteries and these relocated batteries. They're all a pain in the *** to some extent.

 

Also, let me clarify. There are a few things here.

One is using a small batter/undersized battery compared to the stock one, whether it's lead acid or some other type.

Another is relocating the battery, which naturally adds resistance to the electrical system due to longer wire.

The third thing is using a lithium ion battery. Lithium ion batteries have individual cells inside that need to be maintained and balanced. For an actual passenger car electrical system, that presents a problem. Either the alternator/charging system is designed for the battery (to maintain state of charge and balancing of cells inside), or the battery is designed for the charging system. Since this is a 90s car, the charging system does not have a current sensor or control by the ECU like a modern car (which are meant to optimize fuel consumption by minimizing battery charging by the alternator).

You have to have a lithium ion battery that is specifically designed to be used in a passenger car with an old style charging system.

 

just as an FYI here are the battery specs.
Japan uses their own battery sizing (JCI?) and we use our American sizing (BCI).
the original battery is a 65D23L either GS or Panasonic with 420cca, 43Ah
Mazda USA gives you an Interstate 26R with 540cca

IMO, when you replace the battery, you should match or exceed the OE spec, unless its a competition car

 

The car came with a Shorai battery and I purchased a backup after looking at the specs. The battery shows 540cca, so figured I was ok. I didnt take into account Argx's point about old alternator charging technology vs lithium Ion battery. I do hook the car up to the trickle charger every time I pull it into the garage just in case.

 

I mean I'm not going to tell people what to do with their cars... all I'm saying is the more you deviate from the stock charging system, the more hassles you are going to have to deal with. It just comes with the territory.

 

In my case the batt has been relocated. I am trying my best to do the minimum to get my results. The cable I just installed did help eliminate a lot of the dips. I believe one straight to the fuse bus will complete it!! Time to start enjoying the car. 14psi feels pretty badass!

 

So I finished the wire from batt direct to fuse block and it finished the voltage issue! When hot it will jump around .3v or so throughoutthe rev range, but it has not dipped under 14.0 so I consider the case closed. I cranked the stereo with some lights on and it still held. I can now put my foot down whenever I want and my mind is at ease. Very happy!!! Car feels awesome and pulls very hard.

 

Nice!

Can you list out how you have everything set up at this point? This would be a good how-to for fixing voltage problems.

Dale

 

I had originally let Pettit do a battery relocation to the bin so I could fit their large IC. They put in a wheel chair battery with a 6 guage wire to the starter and factory hookups from there. Possibly adequate for a stock set up. I also had Pettit's airpump removal pulley so the alternator was under driven a bit.

I kept their original wire and added a 6 guage from the battery directly to the alternator charging post and another from the battery directly to the fuse block. The battery was swapped out with a 51R.

Grounds were beefed up and used in stock locations and I added a few. The typical "RX7 grounding kit" talked about like on FD3s.net. I used high quality JL audio wire for the "grounding kit" and used welding wire for the larger grounds. The one large ground wire I added was simply to the seat post bolt on the passenger side.

I installed a "booster" diode to the alternator sensing wire which will boost the voltage up around .5 volts. That was sourced from HKB Electronics. Splice a micro fuse holder in line and simply install the " fuse" diode in.

​​​chanIRP's "upgraded" alternator also.
I changed out the positive terminal with a multi point one. I will change the negative terminal out also. My fuel pump is wired directly to the battery.
I truly hope this helps anyone that may run into the same problem.

Dale I could write up a better thread later labeled "how I fixed my low voltage" with more detail.

I am trying to get on the dyno today, but they are not answering me!!!
Who doesn't like to hear a rotary screaming? They should put me in front!!

 

The "booster" diode sounds interesting.

 

I think it is very interesting and I see nothing wrong with it. I have an adjustable one, but I would think the "normal one" HKB sells would be good. I have one on the way and will swap them out and see how it goes. On cold start up it may be around 14.6 jumping to 14.8 a few times, but settles down to mid 14s. Then once warmed up 14.0-14.6 volt with an average if around 14.3 maybe.


I just feel much better when I turn the lights on or crank the stereo. Or both. It still jumps around quite a bit, but from what I have gathered from a few that is quite normal. No dips below 14 at high boost high rpm anymore..
I consider this complete. I may install a voltage stabilizer down the road, but I will think about it a bit more.